XML 133 R123.htm IDEA: XBRL DOCUMENT
v3.21.1

Commitments and contingencies - Financial Instruments with Off-Balance Sheet Credit Risk (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Balance at end of period | $ 2,787,594 | $ 1,105,742
Commitments to extend credit, excluding interest rate lock commitments |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Balance at end of period | 2,719,996 | 1,086,173
Letters of credit |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Balance at end of period | $ 67,598 | $ 19,569

X
- Definition The face amount of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition. + References No definition available. + Details
Name: | us-gaap_FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CommitmentsToExtendCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=fbk_CommitmentsUnderLetterOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |